Progress in homogeneous catalysis including homogeneous hydrogenation often involves the development of novel ligands and their transition-metal complexes that are active as pre-catalysts or catalysts. The vast majority of ligands used in homogeneous catalysis are based on P and/or N donor atoms and an enormous number of such bi-, tri- and tetradentate ligands have been designed and synthesized over the past half century.
As understood, polydentate chelating ligands bearing N—H functionalities play a crucial role in a conventional bifunctional metal-ligand (i.e., M/NH) molecular catalysis, in which the ligand facilitates the catalytic reaction via stabilization of rate-determining transition states, for example, through N—H . . . O hydrogen bonding interactions and/or an N—H bond cleavage/formation, respectively. The bifunctional molecular catalysis based on metal-ligand (M/NH) cooperation was originally developed for asymmetric hydrogenation chemistry (e.g. Noyori asymmetric hydrogenation) and transfer hydrogenation of ketones and imines, and is now applicable to a variety of chemical transformations with a wide scope and high practicality. For example, the chemical transformations include, but are not limited to, practical hydrogenation of carboxylic and carbonic acid derivatives, hydrogenation and electroreduction of CO2, reductive transformation of CO2 into methanol (for a methanol based economy), various acceptorless dehydrogenations, asymmetric Michael reactions of 1,3-dicarbonyl compounds with cyclic enones and nitroalkenes, stereoselective catalytic C—N and C—C bond-forming reactions, aerobic oxidative kinetic resolution of racemic secondary alcohols, asymmetric hydration of nitriles and others.
Given the utility of these catalysts (representative examples from Takasago Int. Corp. are: RUCY-XylBINAP: a) Hori et al., Published Patent WO/2012/137460A1 by Takasago International Corporation for “Novel Ruthenium Complex and Process for Producing Optically Active Alcohol Compound Using the Same as Catalyst”; (b) Matsumura et al., “Chiral Ruthenbicyclic Complexes: Precatalysts for Rapid, Enantioselective, and Wide-Scope Hydrogenation of Ketones” J. Am. Chem. Soc. 2011, 133, 10696; and (c) Ohkuma et al., U.S. Pat. No. 9,328,079 by Takasago International Corporation for “Process for Producing Optically Active Amine”; Ts-DENEB: (a) Tanaka et al., Published Patent WO/2013/065867A1 by Takasago International Corporation for “Method for Producing Optically Active Beta-Hydroxy-alpha-Aminocarboxylic Acid Ester”; (c) Touge et al. Published Patent WO/2012/144650A1 by Takasago International Corporation for “Method for Producing Compound with Carbonyl Group Using Ruthenium Carbonyl Complex having Tridentate Ligand as Dehydrogenation Oxidation Catalyst”; (d) Touge et al., “OxoOTehered Ruthenium (II) Complex as a Bifunctional Catalyst for Asymmetric Transfer Hydrogenation and H2 Hydrogenation” J. Am. Chem. Soc. 2011, 133, 14960; (e) Touge, T.; Nara, H.; Fujiwhara, M.; Kayaki, Y.; Ikariya, T. J. Am. Chem. Soc. 2016, 138, 10084; and (f) Touge et al., Published Patent WO/2012/026201A1 by Takasago International Corporation, for “Ruthenium-Diamine Complexes and Method for Producing Optically Active Compounds”; Ru-MACHO: (a) Touge et al. U.S. Pat. No. 9,000,212B2 by Takasago International Corporation, for “Method for Producing Compound with Carbonyl Group using Ruthenium Carbonyl Complex having Tridentate Ligand as Dehydrogenation Oxidation Catalyst”; (b) Hori et al. for “Method for reducing halogenobenzoic acid ester using ruthenium carbonyl complex” by Takasago International Corporation, US Published Patent 20140163257A1 (c) Kuriyama et al. for “Preparation of ruthenium carbonyl complexes having tridentate aminodiphosphine ligand as reductive hydrogenation catalysts”. Published Patent WO/2011/048727A1; (d) Kuriyama, W. et al. for “Catalytic hydrogenation of esters. Development of an efficient catalyst and processes for synthesizing (R)-1,2-propanediol and 2-(1-methoxy)ethanol.” Org. Process Res. Dev. 16, 166-171, (2012); (e) Ogata et al. for “Atmospheric Hydrogenation of Esters Catalyzed by PNP-Ruthenium Complexes with an N-Heterocyclic Carbene Ligand.” Org. Lett. 18, 3894-3897, (2016); and (f) Ogata et al. for “Preparation of ruthenium complexes having bis(phosphinoalkyl)amine and N-heterocyclic carbene ligands, organic reaction catalysts containing them, and their use”. Published Patent WO/2015/163440A1 (2015)), there is interest in further ligand and catalyst design.

As such, there exists a continued need for developing novel ligand and catalyst design.